Segment Information (Summary Of Segment Information) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Segment Reporting Information [Line Items]
Revenues	$ 519,508	$ 498,681	$ 1,020,729	$ 981,483
Operating Income	36,913	29,553	62,885	62,040
Truckload Transportation Services
Segment Reporting Information [Line Items]
Revenues	403,502	379,249	788,505	752,166
Operating Income	36,036	22,766	59,502	55,125
Werner Logistics
Segment Reporting Information [Line Items]
Revenues	100,804	103,965	200,657	200,542
Operating Income	2,285	6,573	5,334	11,608
Other Segment
Segment Reporting Information [Line Items]
Revenues	15,127	15,166	31,237	28,344
Operating Income	(541)	(1,839)	(396)	(3,773)
Corporate Segment
Segment Reporting Information [Line Items]
Revenues	524	614	946	987
Operating Income	(867)	2,053	(1,555)	(920)
Subtotal
Segment Reporting Information [Line Items]
Revenues	519,957	498,994	1,021,345	982,039
Intersegment Elimination
Segment Reporting Information [Line Items]
Revenues	$ (449)	$ (313)	$ (616)	$ (556)